The present invention generally relates guidewires used in vascular surgery and procedures, and specifically to angioplasty and embolectomy guidewires.
Guidewires are used in various surgical catheter procedures to steer a catheter to a desired location in the patient's vascular system. Generally, the guidewires are inserted and steered through the patient's vascular system to the desired site. The catheter is typically positioned over a portion of the guidewire during this initial placement, and then pushed along the guidewire until properly positioned at the desired site. Standard guidewires are typically longer than the catheter to allow for independent movement of the catheter and the wire. Examples of suitable guidewires are illustrated in U.S. Pat. No. 4,538,622, issued to Samson et al on Sep. 3, 1985; U.S. Pat. No. 4,719,924, issued to Crittenden et al on Jan. 19, 1988; U.S. Pat. No. 4,934,380, issued to de Toledo on Jun. 19, 1990 and European Patent Application Number 89304257.2, published on Dec. 20, 1989.
In one particular surgical application, angioplasty, the guidewire is steered to the vascular blockage. Usually the steering of the guidewire is facilitated by a video X-ray device allowing the surgeon to visually observe the movement of the guidewire. The guidewire usually includes a radiopaque marker at its distal end to provide a reference for the surgeon. The surgeon positions the radiopaque marker adjacent the blockage, and then slides a balloon angioplasty catheter over the wire to the blockage.
Generally the balloon is expanded to open the blockage and then is removed along with the guidewire. However, sometimes the balloon breaks, or a larger sized balloon is required to fully open the blockage. In either situation the balloon catheter must be removed, and a replacement catheter is slid over the guidewire.
It is usually desirable to maintain the guidewire in the patient to reduce the time required to reposition the balloon at the blockage. The initial placement of the balloon and wire requires extensive manipulation of the guidewire, and removal and repositioning of the wire is time consuming, and in certain circumstances undesirable.
When required, the surgeon removes the catheter over the guidewire, retaining the wire in the patient. To facilitate the easy removal and replacement of the balloon catheters the guidewire must be sufficiently long enough to allow the surgeon to grip a portion of the wire as the catheter is being withdrawn. This requires the guidewire be long enough to provide an external portion longer than the catheter. However, a wire this long is difficult to steer, and as a result, guidewires are usually only slightly longer than the typical balloon catheter, e.g. 20-50 centimeters.
One previous method used to allow for the exchange of balloon catheters involved replacing the original guidewire with a longer guidewire, and then removing and replacing the catheter. This approach proved to be tedious.
A more recent development involves coupling a length of a second wire to the exposed guidewire end. The second wire length should be sufficient to allow the catheter to be withdrawn while retaining the placement of the guidewire in the patient. Various approaches have been suggested for affecting this coupling action.
United Kingdom Patent Application Number 8615949, published Apr. 1, 1987, corresponding to U.S. Pat. No. 4,917,103, issued to Gamble et al on Apr. 17, 1990, discloses a guidewire extension wire with a tubular connector fitted to the end of either the exposed guidewire or the extension wire. The other wire is formed with a reduced diameter end which slips into the tubular connector. To enhance the fit, Gamble et al discloses crimping the tubular connector. The basic disadvantage to this approach is that the tubular connector does not sufficiently grip the reduced diameter end of the wire unless crimped to prevent dislodging of the guidewire from the extension during the catheter exchange. Crimping of the tubular connector is not reversible requiring the extension wire to be cut off the guidewire exposed end. U.S. Pat. No. 4,922,923, also issued to Gamble on May 8, 1990, teaches the method of connecting the guidewire and extension wire with the described tubular connector.
A variation of the Gamble et al approach is disclosed in U.S. Pat. No. 4,827,941, issued to Taylor et al on May 9, 1989. Again an extension wire is affixed to the exposed proximal end of the guidewire using a tubular connector affixed to the end of either the guidewire or the extension wire. However, the mating end of the guidewire or extension wire is formed to frictionally engage the interior of the tubular connector. This is accomplished by providing the mating end as an undulating smaller diameter segment. While this approach overcomes the need to crimp the tubular connector, there remains the potential of disengagement between the tubular connector and the undulating segment during the catheter exchange procedure.
A modification to the friction approach suggested by Taylor et al is disclosed in U.S. Pat. No. 4,875,489, issued to Messner et al on Oct. 24, 1989. Messner et al discloses the use of two coaxially tubular connectors mounted at either the guidewire proximal end, or the extension wire connecting end. The innermost tubular connector is formed with a longitudinal slot allowing for expansion of the connector diameter as a reduced diameter portion of the other wire is inserted. The outer tubular connector limits the extent of this expansion and reinforces the overall structure. This approach has the disadvantage of disengagement during the catheter exchange procedure.
An approach similar to Messner et al is disclosed in European Patent Application 89304257.2, published on Dec. 20, 1989. In this approach a coil spring is mounted about the reduced diameter portion of either wire. This end is inserted into a tubular connector mounted to the end of the other wire and the insertion into the tubular connection causes at least some of the coil turns to engage in light interference with the internal surface of the tubular connector. This interference longitudinally stretches and constricts the coil, allowing insertion into the tubular connector. Once fully inserted the coil returns to an unconstricted state to grip inside the connector. The main disadvantage of this device is that disengagement requires simultaneous turning and pulling of the connection to compress the spring to enable dislodging from the tubular connector.
U.S. Pat. No. 4,846,193 to William S. Tremulis et al. describes an extendable guidewire which permits the introduction and exchange of catheters. The guidewire of the '193 Tremulis patent has a telescopically mounted inner shaft or wire having axially extended and retracted positions.
Commercially available devices similar to those disclosed in European Patent Application 89304257.2 and Taylor et al possess tubular connectors of larger diameters than the associated wire. One system is the DOC.TM. Guide Wire Extension by Advanced Cardiovascular Systems, Inc., 26531 Ynez Road, Temecula, Calif. The DOC.TM. Guide wire extension is similar in design to that described in Taylor et al (U.S. Pat. No. 4,827,941) A second system, the LINX.TM. Guide Wire Extension by USCI Division of C.R. Bard, Inc., 129 Concord Road, Billerica, Mass. is similar in design to the devices disclosed in the European Patent Application 89304257.2. The larger diameter connector requires that the catheter, which is being passed over the guidewire, possess a larger internal diameter than would be necessary to fit over the smaller diameter guidewire.
The disadvantage of the use of a larger diametered connector is also found with devices made in conformance with Gamble et al, and enhanced when the tubular connector is crimped.
Another worker has suggested the use of female and male threaded body connectors to interconnect the guidewire and extension wire, see U.S. Pat. No. 4,966,163, issued to Kraus et al on Oct. 30, 1990. This device includes an internally threaded female portion in which is fit an externally threaded male portion. A preferred embodiment requires that either the female or male portion be rotatably mounted to the associated wire to allow free rotation. This free rotation assists in the ability to thread the two portions together.
A disadvantage with the Kraus et al device is the fabrication of the female and male threaded sections. The actual size of the connectors is relatively small, i.e. less than 2.3 millimeters. It is difficult to fabricate female and male threaded portions of this size. If the size of the connectors is increased over the diameter of the guidewire and extension wire, the disadvantages discussed above for the DOC.TM. and LINX.TM. Guide Wire Extension systems apply.
It is thus apparent that the need remains for a suitable guidewire extension system using an extension wire which is reliably connected to the guidewire without the described disadvantages.